Midges tough insects

February 10, 2012

One nice day early this week, I took a walk beside a lake. Suddenly, I found myself accompanied by a cloud of tiny gnats that hovered just above my head. I use the word "gnat" here as a generic term, which just means some sort of little fly. When I walked, they flew along with me; when I stopped, they stopped. They did not attempt to fly into my eyes or bite me.

These insects were nonbiting midges, minute true flies in the Family Chironomidae. There are also biting midges known as no-see-ums, Family Ceratopogonidae, but they are different creatures. People often ask me how to tell a biting midge from a nonbiting midge, since they are much too small to identify on sight. The answer is very simple - if it bites you, it is a biting midge! Both types of midges are found around water because their larvae are generally aquatic, although some live in habitats that are simply damp, such as moist mosses.

I am only going to discuss the nonbiting midges today.

You will often see clouds of these minute flies hovering over some upright object that stands out from its surroundings. It might be a tree, a bush, a fence post or, in my case, a person. It is simply serving as a landmark so that many midges can gather in one spot. As with so many things in the natural world, the cloud of midges is about mating. It is a swarm of male midges.

Since midges are extremely small, it is easier to see them when they are in a swarm. And the object, of course, is to be noticed by females. The swarm of males flies up and down with a particular motion that females recognize as belonging to their species. Females fly into the swarm to find mates.

Adult midges have very short lives, and many are believed not to feed at all. Some have been observed visiting flowers for nectar or feeding on the sugary secretions of aphids. Larvae of various species have different diets. Some eat aquatic plants, algae or decaying aquatic plant matter. Others are predators of tiny aquatic creatures.

Midge larvae are very adaptable and are able to thrive in all sorts of watery habitats, including some in which no other insects can survive. They are very tolerant of polluted water, including oxygen-starved areas with fertilizer or sewage runoff. Some Chironomid larvae are red and are known as bloodworms. This leads people to believe that they are blood-suckers, but they are not. They are among the extremely rare insects that have hemoglobin in their blood, just as we do. Hemoglobin allows them to absorb oxygen from oxygen-poor water.

Most Chironomid larvae live in fresh water, with some species preferring running water while others live in still water. Some live in water so shallow that it is only a film a few millimeters deep, such as on top of barely submerged rocks. There are even species that live inside the water-filled traps of carnivorous plants, such as pitcher plants, but are not digested by the plants.

Some midges live in truly extreme habitats. Some species live in salt water of tidal pools and lagoons. Some species live in the water (104-plus degrees F) of hot springs. Others live in temporary pools in arid areas and go into "suspended animation" when their pools dry up, reviving when it rains. Some can survive dessication, and in that state survive temperatures from -454 degrees F to 215 degrees F. Some have survived over a year in outer space. A species that lives on Antarctica is that continent's only insect, and it can survive freezing and exposure to salt water spray.

Midges are extremely interesting insects and are an important part of the ecosystem, serving as food for many fish and other aquatic creatures.

- Send your insect questions to Claire Stuart by email at buglady@wv.net or write her (with self-addressed stamped envelope) in care of Living Section, The Journal, 207 W. King St., Martinsburg, WV 25401.